The present invention relates generally to methods of laying railroad track, apparatus therefor, and, in a preferred embodiment thereof, more particularly provides apparatus for continuous track laying utilizing dual blocks.
Railroad track is typically laid by placing individual rails atop wooden ties which are sequentially spaced orthogonal to the rails. The wooden ties are conventionally embedded atop ballast material intended to stabilize the earth over which the rails traverse. After the rails are placed on the wooden ties they are spaced apart according to the proper "gauge" (lateral spacing between the rails of a track), longitudinally joined to correspondingly spaced rails, and fastened to the wooden ties with spikes.
It is well known in the art to automate the railroad track laying procedure. U.S. Pat. No. 4,232,610 to Theurer discloses an apparatus which lays completed portions of track end to end while the apparatus propels itself on the previously laid track. The completed portions of track include the spaced apart rails fastened to wooden ties.
U.S. Pat. No. 3,713,396 to Colius discloses an apparatus for sequentially spacing and fastening wooden ties to continuous rails. A turntable mechanism is used to drop a tie longitudinally between the rails and then turn the tie so that it is orthogonal to the rails. The tie is then fastened to the spaced apart rails with spikes.
Additionally, it is well known in the art to renew old railroad track rails and/or wooden ties. U.S. Pat. No. 5,357,867 to Theurer et al. discloses an apparatus which renews old railroad track or, if properly configured, lays new track. In order for the new wooden ties to be placed on the ballast, the rails must be widely spaced apart so that the ties will fit transversely between the rails. The apparatus then places the wooden ties on the ballast, gauges the rails, and fastens the rails to the ties. A similar apparatus which includes ballast conditioning features is disclosed in U.S. Pat. No. 4,316,416 to Theurer et al.
For subway applications, a modern technique of laying railroad track utilizes a "dual block" system wherein there are no ties fastened to the spaced apart rails. Instead, the rails are supported on masonry blocks which have elastomeric pads attached to their bottom surfaces for noise and shock suppression. The rails are typically fastened to the blocks, "gauged", and supported up off of grade level so that concrete may be poured around and underneath the blocks, effectively encapsulating the bottoms of the blocks.
Subways are becoming more common as cities grow more congested, and the use of "dual blocks" for supporting rails is increasing as well. The benefits which accrue from the use of blocks instead of ties include reduced noise and shock, and minimal maintenance. The disadvantages of using blocks include increased installation costs.
The above-described process of laying track on blocks is tedious and time-consuming and a need exists for its automation. Unfortunately, none of the existing track laying or renewal apparatus or methods, which were designed for use with wooden ties in an open environment, are suited for laying rails on blocks, nor are they suited for use in the confines of a subway tunnel.
Lateral space is limited in a subway tunnel, so those apparatus which are adapted for spreading of the rails prior to placement of wooden ties therebetween, or picking up of previously spread rails, prior to placement of the rails on wooden ties are unusable therein. Vertical space is also limited in a subway tunnel, so those apparatus which are adapted for lifting track sections or rails over a large structure for placement in front of or behind the large structure are likewise unusable.
Additionally, virtually all of the apparatus adapted for laying track with wooden ties require the apparatus to travel supported, at least in part, on the newly installed track. This cannot be done in dual block installations, which cannot support travel thereupon until the blocks are encapsulated in concrete.
Furthermore, existing apparatus and methods do not take advantage of the unique features available in a modern subway tunnel. For example, electricity and/or compressed air are normally available as sources of power to propel a track laying apparatus. The tunnel, having already been constructed, defines the path the track will follow, and structures therein, such as wiring troughs, may be utilized to provide guidance for a track laying apparatus. In addition, other structures within a tunnel may be utilized for placement of track laying supplies which may be used by the track laying apparatus as it proceeds through the tunnel.
From the foregoing, it can be seen that it would be quite desirable to provide automated track laying apparatus and methods which are suited for the laying of track utilizing dual blocks. Furthermore, such apparatus and methods are needed which may operate in the confines of a subway tunnel. Still further, such apparatus and methods are needed which are adapted to take advantage of the features existing in a modern subway tunnel. It is accordingly an object of the present invention to provide such track laying apparatus and methods.